1. Field of the Invention
The present invention relates generally to ion implantation of plastics and, more particularly, to an ion implantation process for plastics which materially enhances their surface hardness and their resistance to chemical attack.
2. The Prior Art
Ion implantation is a method that was originally developed in the semiconductor industry to effect precise doping of silicon wafers with impurities. From there, the method spread to the ion implantation of metals and compounds, see Treatise on Materials Science and Technology, Vol. 18, "Ion Implantation," 1980, Academic Press, Inc. See also a copending application, assigned to the common assignee herein, entitled "Ion Implantation of Titanium Workpieces Without Surface Discoloration", Ser. No. 861,845, filed May 12, 1986.
In the specific area of ion implantation of plastics, most of the interest and research has focused on advantageously changing the electronic and transport properties of a variety of polymers that are normally insulating. By using masks, for instance, conducting paths in an insulating medium are fabricated. See the article authored by M. S. Dresselhaus et al of M.I.T. "Ion Implantation of Polymers," Mat. Res. Soc. Symp. Proc., Vol. 27 (1984), pp. 413-422. Other workers in the field have studied the reaction of iodine ions with solid alkanes and the effect of carbon ions on benzene. See 7th Int. Hot Atom Chem. Symp. (1973) p. 19, and R. M. Lemmon, id., p. 20. Similar work in organometallic compounds, such as metal carbonyls, has indicated that energetic ions, such as copper and chromium, as well as rare-earth ions, interact with such compounds and that about half of the incoming ions become incorporated in the organometallic chain. See G. K. Wolf, "Ion Bombardment Chemistry," Nucl. Instrum. Methods 139 (1976) 147.
No one to date, as far as known, has however attempted to ion implant plastics, such as used as transparencies in aircraft, safety glasses and face masks, eyeglasses and contact lenses, or non-transparent plastics, such as used in bearings or safety helmets, so as to enhance their surface hardness or their resistance to chemical attack.